A Facile Synthesis and Characterization of Sodium Bismuth Sulfide (NaBiS₂) under Hydrothermal Condition

Abstract

Binary bismuth chalcogenides have received considerable attention for their application in thermoelectric materials; however, there have been relatively fewer reports on the ternary and quarternary bismuth chalcogenides; but nevertheless, a slowly growing number of them can be found. 1Among them, NaCl-type MBiQ 2 (M = Li, Na, K; Q = S, Se) is the most elementary, and was first synthesized 70 years ago in a solid state reaction, and the structures of them have been determined merely by the powder X-ray diffraction method (XRD).2-5 Synthetic methods had been largely limited to molten salt synthesis in a sealed quartz tube for very long reaction time (~9 d) 5, until Qian et al. reported that NaBiS 2 could be isolated as a byproduct, during the synthesis of 1-D bismuth sulfide (Bi 2 S 3 ) nanoribbons, under solvothermal condition (glycerol:water = 2:1). 6,7 In that report, when higher concentration of NaOH is added to the reaction medium, NaBiS 2 is found at the bottom of the autoclave. 6The NaBiS 2 was characterized only by XRD and scanning electron microscopy (SEM), but no other characterization was performed.6 Inspired by this finding, we have tried to synthesize sodium bismuth sulfide as a sole product, in aqueous medium. Herein, we report the synthesis of NaBiS 2 as the sole product by hydrothermal reaction, for the first time. The synthesis produced NaBiS 2 nanosheets, and it was characterized by XRD, diffuse reflectance spectrophotometry, X-ray photoelectron spectroscopy (XPS), and elemental analysis by energy dispersive X-ray spectroscopy (EDX). This synthetic method might open up new opportunities to access NaBiS 2 , and is environmentally benign; it might therefore be utilized in a variety of fields, including thermoelectric materials, and light harvesting materials. Experimental SectionAll the chemicals were of analytical grade, and were used as-received, without further purification. Distilled water was purified by a New P.nix UP 900 water purification system (Human Corporation, South Korea). IR spectra were recorded, using a MIDAC M series spectrometer. Powder X-ray diffraction (XRD) data were collected at 40 kV and 35 mA, using a Philips X'pert MPD diffractometer (Philips Analytical, Netherlands); CuK α radiation was used as the source (λ = 1.5418 Å). Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses were performed, using a Bruker Quantax 200 125ev SEM spectrometer (Germany). X-ray photoelectron spectra (XPS) were recorded, using an ESCALAB 210 X-ray Photoelectron Spectroscope.Synthesis of Sodium Bismuth Sulfide. Synthesis of sodium bismuth sulfide (NaBiS 2 ) was performed by the following procedures: Bi(NO 3 ) 3 ·5H 2 O (40 mM, 4.0 mmol) and L-Cys (120 mM, 12.0 mmol) were mixed to make a 100 mL of aqueous solution, followed by adding NaOH (2.5 M, 0.25 mol). The resulting solution was transferred to a teflon-lined autoclave reactor, and stirred with magnetic stirrer for an additional 30 min. Subsequently, the autoclave reactor was placed in an electric convectio...

Perovskite-inspired materials for photovoltaics and beyond—from design to devices

“…NaBiS2 can be obtained by melt synthesis [194], in which powders of S, Bi, and Na2S are mixed in a sealed tube, followed by a series of heating steps at high temperature for very long reaction time (~9 days). The hydrothermal method [195] can reduce the reaction time by technique [196], where QD sizes can be controlled by different concentrations of the precursor solution. NaBiS2 has been found to have an indirect band gap of about 1.2-1.45 eV, in agreement with computations [25].…”

Identifying defect-tolerant semiconductors with high minority-carrier lifetimes: beyond hybrid lead halide perovskites

“…Similar to the formation of I-III-VI 2 analogues of the zincblende II-VI compounds, one may form I-III-VI 2 rocksalt compounds based on the PbS and PbSe rocksalt phases. [79][80][81] These include Pb-free chalcogenides with an octahedrally-coordinated Bi 3+ cation.…”

NaBiS2 as a Novel Indirect Bandgap Full Spectrum Photocatalyst: Synthesis and Application

“…As shown in Figure 3, the XPS survey spectra reveal that the sample was composed of Bi, S, and Na elements. The peaks located at 290 eV and 530 eV correspond to C and O, which originate from the conducting resin and moisture adsorbed by the sample [23]. Two strong symmetrical peaks, located at 158.3 eV and 163.4 eV in Figure 3b, are attributed to Bi4f7/2 and Bi4f5/2 signals because of the spin-orbit splitting of Bi4f.…”

“…Fabrications with less Na2S or NaOH were also carried out, respectively. As shown in Figure 1b, the formation of NaBiS2 was NaBiS 2 was reported to be synthesized from mixtures of Bi(NO 3 ) 3 and L-cysteine [23], or by a two-step hydrothermal process from Bi(NO 3 ) 3 ·5H 2 O and Na 2 S·9H 2 O [24], both of which were reacted in NaOH aqueous solution. Nevertheless, NaBiS 2 was believed not to be the most stable product in the hydrothermal process.…”